Research on High-Stability Composite Control Methods for Telescope Pointing Systems under Multiple Disturbances

Area of Science:

• Space physics
• Astrophysics
• Control systems engineering

Background:

• Space gravitational wave detectors rely on precise inter-satellite laser links.
• Satellite constellation geometry, crucial for link stability, drifts from ideal configurations due to orbital variations.
• Telescope pointing mechanisms actively compensate for these angular deviations.

Purpose of the Study:

• To propose a high-performance robust composite control method for telescope pointing systems.
• To enhance robust stability, disturbance rejection, and tracking performance.
• To meet stringent pointing stability requirements for space missions.

Main Methods:

• Developed a composite control strategy combining an H-infinity controller and an H-infinity norm optimized disturbance observer (HODOB).
• Designed the H-infinity controller based on the dynamic model of the telescope pointing mechanism and disturbance noise.
• Integrated HODOB to specifically address nonlinear friction and improve disturbance rejection.

Main Results:

• The HODOB method demonstrated an order of magnitude improvement in tracking accuracy and pointing stability compared to traditional disturbance observers (DOB).
• The composite control method significantly enhanced overall system performance.
• Achieved pointing stability meeting the TianQin mission requirement of 10 nrad/Hz^1/2 @0.1 mHz~1 Hz.

Conclusions:

• The proposed robust composite control method is highly effective for stabilizing telescope pointing systems in space missions.
• HODOB offers superior nonlinear friction rejection and disturbance rejection capabilities.
• The method ensures the precise pointing stability necessary for future gravitational wave observatories.